Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$157.53	11.560%	$175.7405	$175.74	$175.75	$175.70
Purchase #2	$133.69	7.200%	$143.3157	$143.32	$143.30	$143.30
Purchase #3	$208.45	4.712%	$218.2722	$218.27	$218.25	$218.30
Purchase #4	$44.94	13.451%	$50.9849	$50.98	$51.00	$51.00
Purchase #5	$83.59	6.123%	$88.7082	$88.71	$88.70	$88.70
Purchase #6	$129.40	9.782%	$142.0579	$142.06	$142.05	$142.10
Purchase #7	$204.33	9.330%	$223.394	$223.39	$223.40	$223.40
7 purchase totals =	$961.93		$1,042.4734	$1,042.47	$1,042.45	$1,042.50